1. Field of the Invention
The present invention relates to a respiration suppressing member which is attached to the body of a subject in order to suppress the respiration-based motion of his or her internal organs and a magnetic resonance imaging apparatus and method using such a respiration suppressing member.
2. Description of the Related Art
In order to produce an image of the coronary artery of a human body (subject) under examination by means of magnetic resonance imaging, an imaging technique is used which, using a three-dimensional steady state free precession (3D SSFP) sequence, produces images of the subject while he or she is intercepting breathing or respiring naturally. In particular, with the whole heart MR coronary angiography (WH MRCA) which visualizes the coronary artery in the whole heart, breathing intercept can provide insufficient spatial resolution. To avoid this problem, a technique is used which, under natural respiration, monitors the respiration-based motion by detecting the location of the diaphragm on the basis of nuclear magnetic resonance (NMR) signals and changes the imaging position to fit the detected respiration-based motion. Further, a technique is used which sets a constant threshold on the range of respiration-based motion and ceases the collection of NMR signals when the motion exceeds that threshold. That is, for example, data collection is made only when the peak of signals resulting from one-dimensional Fourier transform of NMR signals collected from such a region R as shown in FIG. 12A falls in the allowable range between upper and low limiting thresholds USL and LSL as shown in FIG. 12B. In addition, imaging is performed while the imaging position is changed to fit the respiration-based motion.
By so doing, 3D images of considerably high resolution can be obtained even under natural respiration.
The related techniques are known from, for example, JP-A Nos. 2000-041970, 2000-157507, and 2004-057226.
However, when the respiration level is not constant but gradually falls or rises, the portion corresponding to the location of the diaphragm in the signals resulting from one-dimensional Fourier transform of NMR signals will deviate from the allowable range as shown in FIG. 12C. In such a case, the imaging time might be increased. In the worst case, examination could not be completed.
For this reason, as shown in FIG. 13, a belt-like fixing means 500 is used to fix the subject's abdomen. In this case, although the motion of the diaphragm is suppressed, the thorax will also be subjected to pressure. Thus, the subject might breathe with difficulty. Conversely, trying to avoid such a situation results in the effect of suppressing the motion of the diaphragm being lessened.